Battery electrode and manufacturing method and apparatus for the same

ABSTRACT

A workpiece, in which a lead is laid on top of a three-dimensional porous metal body, is placed between an ultrasonic horn and an anvil with a lead portion facing the ultrasonic horn. A support is raised so that the lead portion of the workpiece is pressed between the ultrasonic horn and the anvil. While being rotated around a central shaft with a motor, the ultrasonic horn vibrates at a frequency of 20 kHz in the shaft direction. Thus, the workpiece is advanced continuously, so that the lead is bonded ultrasonically to the three-dimensional porous metal body (i.e., metal-to-metal bonding is established). It is possible to provide a battery electrode that can be produced continuously at a lower running cost, reduce the faulty welding with a current collecting plate, and prevent short-circuits.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a battery electrode produced bybonding a lead to a three-dimensional porous metal body and amanufacturing method and apparatus for the same.

[0003] 2. Description of the Related Art

[0004] A battery electrode usually includes a lead to be connected to apositive electrode terminal or a current collecting plate. This type ofbattery electrode has been manufactured by a resistance seam weldingprocess. Specifically, as shown in FIG. 6, first, a rod-shaped Cuelectrode 22 for welding is brought into contact with a lead 21, whichhas been laid on top of a three-dimensional porous metal body 20. Then,the lead 21 is pressed into close contact with the three-dimensionalporous metal body 20, and a large amount of current flows between thethree-dimensional porous metal body 20, acting as a positive electrode,and the Cu electrode 22, acting as a negative electrode. Thus, the lead21 is spot-welded to the three-dimensional porous metal body 20. Then,the three-dimensional porous metal body 20, to which the lead 21 hasbeen welded, is filled with an active material and rolled. Finally, thethree-dimensional porous metal body 20 thus filled with an activematerial and rolled is cut to a predetermined size, resulting in abattery electrode.

[0005] However, the method for manufacturing a battery electrode by theresistance seam welding process makes continuous production difficultand increases the running cost. This is because the lifetime of the Cuelectrode 22 for welding is short, which requires maintenance atfrequent intervals. Moreover, when the Cu electrode 22 is used as awelding electrode, though the welding performance is improved,sputtering occurs to increase short-circuits because of the inclusion ofCu. In addition, the active material that enters the gap between thelead 21 and the three-dimensional porous metal body 20 during thefilling process remains, so that faulty welding often is caused when thebattery electrode and a current collecting plate are welded together,and short-circuits are increased as well.

SUMMARY OF THE INVENTION

[0006] Therefore, with the foregoing in mind, it is an object of thepresent invention to provide a battery electrode that can be producedcontinuously at a lower running cost, reduce the faulty welding with acurrent collecting plate, and prevent short-circuits, and amanufacturing method and apparatus for the same.

[0007] To achieve the above object, a configuration of a batteryelectrode of the present invention includes an electrode plate and alead bonded to the electrode plate. The entire surface of the leadopposed to the electrode plate is bonded ultrasonically to the electrodeplate. This configuration can provide a battery electrode to which theentire surface of the lead opposed to the electrode plate is bonded, sothat no active material enters the bonding area between the lead and theelectrode plate. When the electrode is cut to a predetermined size, thelead also is cut. Therefore, if any active material has entered thebonding area, the material comes out during cutting. This is likely tocause the faulty welding between the electrode and a current collectingplate. However, the configuration of a battery electrode of the presentinvention is such that no active material enters the bonding areabetween the lead and the electrode plate, so that the faulty welding canbe reduced.

[0008] In the configuration of a battery electrode of the presentinvention, it is preferable that the electrode plate is athree-dimensional porous metal body, and that the lead is bonded to oneedge portion of the three-dimensional porous metal body.

[0009] In the configuration of a battery electrode of the presentinvention, it is preferable that the entire surface of the electrodeplate is patterned by applying pressure, to which the lead is bonded.Those patterns can be used to judge whether the bonding strength isoptimized or whether the uniformity of bonding is maintained over thelead surface.

[0010] A method for manufacturing a battery electrode of the presentinvention includes bonding a lead to an electrode plate. In this methodfor manufacturing a battery electrode, a three-dimensional porous metalbody is used as the electrode plate, and the lead is continuously bondedultrasonically to the three-dimensional porous metal body, which then isfilled with an active material and rolled. According to this method formanufacturing a battery electrode, the entire surface of the leadopposed to the three-dimensional porous metal body can be bondedcontinuously thereto. As a result, no active material enters the bondingarea between the three-dimensional porous metal body and the lead duringthe filling and rolling processes. Thus, the faulty welding between theelectrode and a current collecting plate can be reduced.

[0011] In the method for manufacturing a battery electrode of thepresent invention, it is preferable that any excess active material isremoved after the filling and rolling processes. According to thispreferred example, the excess active material that adheres to the leadportion and the surface of the three-dimensional porous metal body canbe removed. Therefore, the faulty welding between the final batteryelectrode and a current collecting plate can be reduced, andshort-circuits can be prevented as well. In this case, the excess activematerial is removed preferably by spraying air. According to thispreferred example, the excess active material can be removed easily.Also, the same effect can be obtained by brushing. In this case, it isfurther preferable that the removed excess active material is collectedby suction.

[0012] An apparatus for manufacturing a battery electrode of the presentinvention includes an ultrasonic horn and an anvil. The ultrasonic hornis in the form of a disk, and can rotate around a central axis andvibrate in the central axis direction. The anvil is in the form of adisk, arranged opposing the ultrasonic horn on the same plane, and canrotate around a central axis. The ultrasonic horn and the anvil moverelative to each other so that the circumferential surfaces of theultrasonic horn and the anvil can be pressed together to make contactcontinuously. The apparatus for manufacturing a battery electrode havingthe above configuration is provided with the disk-shaped ultrasonic hornand anvil. Therefore, a hoop material can be used as a workpiece, i.e.,the material to be welded is supplied continuously from a roll. As aresult, battery electrodes can be produced continuously by supplying thehoop material, thereby reducing the running cost.

[0013] In the configuration of the apparatus for manufacturing a batteryelectrode of the present invention, it is preferable that the anvil hasconcavities and convexities formed on the circumferential surfacethereof. According to this preferred example, the function of holding aworkpiece can be enhanced. In this case, it is preferable that thesurface area of the convexities is 10% to 50% of the overall occupiedarea of the circumferential surface of the anvil. Also, in this case, itis preferable that the circumferential surface of the anvil is coatedwith ceramic or plated with nickel. Moreover, in this case, a depth ofthe concavities preferably is in the range of 20 μm to 100 μm.

[0014] In the configuration of the apparatus for manufacturing a batteryelectrode of the present invention, it is preferable that the ultrasonichorn has a flat circumferential surface. This preferred example canimprove the maintenance of the ultrasonic horn and increase the lifetimethereof, so that the efficiency of the continuous production of batteryelectrodes is improved.

[0015] In the configuration of the apparatus for manufacturing a batteryelectrode of the present invention, it is preferable that a width of thecircumferential surface of the ultrasonic horn is the same as that ofthe anvil, and that both edges of the circumferential surfaces of theultrasonic horn and the anvil are cut off. According to this preferredexample, since the abrasion of the ultrasonic horn and the anvilproceeds simultaneously, the lifetime of the apparatus can be made stilllonger. Moreover, this preferred example can prevent the vicinity of thelead portion from being cut when the lead portion of the workpiece ispressed between the ultrasonic horn and the anvil.

[0016] As described above, the present invention can provide a batteryelectrode that can be produced continuously at a lower running cost,reduce the faulty welding with a current collecting plate, and preventshort-circuits.

[0017] These and other advantages of the present invention will becomeapparent to those skilled in the art upon reading and understanding thefollowing detailed description with reference to the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 shows a configuration of an ultrasonic bonding apparatus(ultrasonic welder) to be used in an embodiment of the presentinvention.

[0019]FIG. 2 is a cross-sectional view showing the shape of thecircumferential surface of an anvil in the ultrasonic boding apparatusof FIG. 1.

[0020]FIG. 3 is a schematic view showing a three-dimensional porousmetal body and a lead, which are bonded together using the ultrasonicbonding apparatus of FIG. 1.

[0021]FIG. 4 is a schematic view showing a process of removing excessactive material.

[0022]FIG. 5 is a plan view showing a battery electrode produced by amanufacturing method of an embodiment of the present invention.

[0023]FIG. 6 is a schematic view showing a process of manufacturing abattery electrode plate according to the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the present invention will be described morespecifically by the use of an embodiment.

[0025] In this embodiment, a three-dimensional porous metal body thatacts as an electrode plate and a lead are bonded ultrasonically byutilizing ultrasonic vibration (i.e., metal-to-metal bonding isestablished). FIG. 1 shows a configuration of an ultrasonic bondingapparatus (ultrasonic welder) to be used in this embodiment. FIG. 2 is across-sectional view showing the shape of the circumferential surface ofan anvil in the ultrasonic bonding apparatus. FIG. 3 is a schematic viewshowing a three-dimensional porous metal body and a lead, which arebonded together using the ultrasonic bonding apparatus. FIG. 4 is aschematic view showing a process of removing an excess active material.FIG. 5 is a plan view showing a battery electrode produced by amanufacturing method of this embodiment.

[0026] As shown in FIG. 1, an ultrasonic bonding apparatus 1 includes anultrasonic horn 2 and an anvil 3 as basic components; the anvil 3 isplaced under the ultrasonic horn 2.

[0027] The ultrasonic horn 2 is in the form of a disk having a diameterof 240 mm and a thickness (width) of 8 mm, rotated around a centralshaft 4 with a motor 17, and supported movably in the shaft direction. Avibrator 5, which can generate ultrasonic vibration of longitudinalwaves with a frequency of 20 kHz, is connected to the central shaft 4.This allows the ultrasonic horn 2 to vibrate at amplitude of 12 μm inthe shaft direction. The amplitude of the ultrasonic horn 2 can varyfrom 11.1 μm to 30 μm.

[0028] The anvil 3 is in the form of a disk having a diameter of 60 mmand a circumferential surface width of 8 mm, and supported rotatably bya support 7 via a central shaft 6. Here, the anvil 3 and the ultrasonichorn 2 are arranged on the same plane opposing each other. Also, theanvil 3 can rotate around the central shaft 6. The support 7 issupported by a base 8 so as to move up and down and is connected to anair cylinder 9 at the lower face thereof. Moreover, a pressure gage 10for measuring air pressure is connected to the air cylinder 9. Aworkpiece 11, in which a lead is laid on top of a three-dimensionalporous metal body (Ni), is placed between the ultrasonic horn 2 and theanvil 3 with a lead portion facing the ultrasonic horn 2. Then, thesupport 7 is raised so that the lead portion of the workpiece 11 ispressed between the ultrasonic horn 2 and the anvil 3. At this time, theapplied pressure is 940 N (the air pressure is 0.20 MPa and the totalmass of the anvil, the central shaft, and the support is 12 kg). Thespeed of supplying the workpiece 11 is 10 m/min.

[0029] As described above, since this embodiment provides thedisk-shaped ultrasonic horn 2 and anvil 3, a hoop material can be usedas the workpiece 11. As a result, battery electrodes can be producedcontinuously by supplying the hoop material, thereby reducing therunning cost.

[0030] As shown in FIG. 2, the anvil 3 has geometrically arrangedconcavities and convexities on the circumferential surface to enhancethe function of holding the workpiece 11. Such unevenness is formed byetching, an electrodeposition process, or machining. Here, it isdesirable that the surface area of the convexities is 10% to 50% of theoverall occupied area of the circumferential surface of the anvil 3.When the surface area is below 10% or above 50% of the overall occupiedarea of the circumferential surface of the anvil 3, the function ofholding the workpiece 11 is lowered, which is undesirable. In thisembodiment, the surface area of the convexities is set to 20% of theoverall occupied area of the circumferential surface of the anvil 3.Moreover, it is desirable that the depth of the concavities is in therange of 20 μm to 100 μm. The depth less than 20 μm is undesirablebecause the function of holding the workpiece 11 is lowered. Also, thedepth more than 100 μm is undesirable because it becomes difficult tocollect the active material entering the concavities formed in athree-dimensional porous metal body after the convexities of the anvil 3have been transferred. Even if the anvil 3 has the concavities with adepth more than 100 μm, it will not so much affect the function ofholding the workpiece 11. In this embodiment, the depth of theconcavities is set to 80 μm. Furthermore, the uneven circumferentialsurface of the anvil 3 is coated with ceramic or plated with nickel toprevent the adhesion of a three-dimensional porous metal body (Ni).

[0031] The ultrasonic horn 2 has a flat circumferential surface toimprove the maintenance. This can increase the lifetime of theultrasonic horn 2 and the efficiency of the continuous production ofbattery electrode plates. In this embodiment, particularly, the width ofthe ultrasonic horn 2 is the same as that of the anvil 3, and thus theabrasion of the ultrasonic horn 2 and the anvil 3 proceedssimultaneously. Therefore, the lifetime of the apparatus can be madestill longer. Moreover, increasing the pressure applied by the anvil 3ensures that the lead portion is held.

[0032] Furthermore, both edges of the circumferential surfaces of theultrasonic horn 2 and the anvil 3 are cut off to have a round surface (Rsurface) or a small chamfered surface (C surface), as shown in FIG. 3.This can prevent the vicinity of the lead portion from being cut whenthe lead portion of the workpiece 11 is pressed between the ultrasonichorn 2 and the anvil 3.

[0033] Next, a method for manufacturing a battery electrode using theultrasonic bonding apparatus having the above configuration will bedescribed.

[0034] First, a three-dimensional porous metal body 12 made of Ni andhaving a width of 150 mm is prepared.

[0035] Then, a lead 13 having a width of 6 mm is passed through a guide(not shown) and laid on top of a predetermined area of thethree-dimensional porous metal body 12, resulting in a workpiece 11.

[0036] The workpiece 11 is placed between the ultrasonic horn 2 and theanvil 3 with a lead portion facing the ultrasonic horn 2. Then, thesupport 7 is raised so that the lead portion of the workpiece 11 ispressed between the ultrasonic horn 2 and the anvil 3.

[0037] Next, while being rotated around the central shaft 4 with themotor 17, the ultrasonic horn 2 vibrates in the shaft direction. Thisallows the workpiece 11 to be advanced continuously, so that the entiresurface of the lead 13 opposed to the three-dimensional porous metalbody 12 is bonded ultrasonically to the predetermined area of thethree-dimensional porous metal body 12 (i.e., metal-to-metal bonding isestablished), as shown in FIG. 3. In this embodiment, since theultrasonic bonding apparatus 1 is used for bonding the lead 13 to thethree-dimensional porous metal body 12, the entire surface of the lead13 opposed to the three-dimensional porous metal body 12 is bondedthereto. As a result, no active material enters the bonding area betweenthe three-dimensional porous metal body 12 and the lead 13 in thesubsequent processes, including filling the workpiece with an activematerial and rolling it. Thus, the faulty welding between the finalelectrode and a current collecting plate can be reduced. In addition, awelding electrode is not used, which can prevent sputtering andshort-circuits caused by the inclusion of Cu or the like. In this case,it is desirable that the entire surface of the three-dimensional porousmetal body 12 is patterned, e.g., with projections or the like byapplying pressure, to which the lead 13 is bonded. Those patterns can beused to judge whether the bonding strength is optimized or whether theuniformity of bonding is maintained over the lead 13 surface.

[0038] Then, the three-dimensional porous metal body 12, to which thelead 13 has been bonded, is filled with an active material and rolled.

[0039] After the filling and rolling processes, air is sprayed on thethree-dimensional porous metal body 12 around the lead 13 portion, asshown in FIG. 4. In such a manner, the excess active material thatadheres to the lead 13 portion and the surface of the three-dimensionalporous metal body 12 is removed. As a result, the faulty welding betweenthe final battery electrode and a current collecting plate can bereduced, and short-circuits can be prevented as well. In this case, theuse of an apparatus provided with a suction nozzle 14 having a diameterlarger than the width of the lead 13 and an injection nozzle 15 housedin the suction nozzle 14 allows the excess active material to be removedand collected at the same time. Thus, efficient operations can beachieved.

[0040] Finally, the workpiece 11, from which the excess active materialhas been removed and collected, is cut to a width of 35 mm and a lengthof 80 mm. This results in a battery electrode 16 having the lead 13 onone edge portion thereof, as shown in FIG. 5.

[0041] In a method for manufacturing a battery electrode of the presentinvention, the entire surface of a lead opposed to an electrode plate isbonded to the electrode plate. Thus, a burr that occurs when the leadpeels off during cutting can be suppressed. Moreover, since the lead isprovided on one edge portion of the electrode plate, a battery electrodehaving an excellent efficiency of collecting current can be manufacturedeasily.

[0042] In this embodiment, air is sprayed to remove any excess activematerial. However, the present invention is not limited thereto. Forexample, a brush may be used instead of the injection nozzle 15 in FIG.4.

[0043] In this embodiment, the workpiece 11 is placed between theultrasonic horn 2 and the anvil 3 with the lead portion facing theultrasonic horn 2. However, the present invention is not limitedthereto, and the workpiece 11 may be placed between the ultrasonic horn2 and the anvil 3 with the lead portion facing the anvil 3.

[0044] The invention may be embodied in other forms without departingfrom the spirit or essential characteristics thereof. The embodimentsdisclosed in this application are to be considered in all respects asillustrative and not limiting. The scope of the invention is indicatedby the appended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

What is claimed is:
 1. A battery electrode comprising: an electrodeplate, and a lead bonded to the electrode plate, wherein an entiresurface of the lead opposed to the electrode plate is bondedultrasonically to the electrode plate.
 2. The battery electrodeaccording to claim 1 , wherein the electrode plate is athree-dimensional porous metal body, and the lead is bonded to one edgeportion of the three-dimensional porous metal body.
 3. The batteryelectrode according to claim 1 or 2 , wherein an entire surface of theelectrode plate is patterned by applying pressure, to which the lead isbonded.
 4. A method for manufacturing a battery electrode comprising:bonding a lead to an electrode plate, wherein a three-dimensional porousmetal body is used as the electrode plate, and the lead is continuouslybonded ultrasonically to the three-dimensional porous metal body, whichthen is filled with an active material and rolled.
 5. The methodaccording to claim 4 , wherein excess active material is removed afterthe filling and rolling processes.
 6. The method according to claim 5 ,wherein the excess active material is removed by spraying air.
 7. Themethod according to claim 5 , wherein the excess active material isremoved by brushing.
 8. The method according to claim 6 or 7 , whereinthe removed excess active material is collected by suction.
 9. Anapparatus for manufacturing a battery electrode comprising: anultrasonic horn in the form of a disk, capable of rotating around acentral axis and vibrating in a central axis direction, and an anvil inthe form of a disk, arranged opposing the ultrasonic horn on a sameplane, and capable of rotating around a central axis, wherein theultrasonic horn and the anvil move relative to each other so that thecircumferential surfaces of the ultrasonic horn and the anvil can bepressed together to make contact continuously.
 10. The apparatusaccording to claim 9 , wherein the anvil has concavities and convexitiesformed on the circumferential surface thereof.
 11. The apparatusaccording to claim 10 , wherein the circumferential surface of the anvilis coated with ceramic or plated with nickel.
 12. The apparatusaccording to claim 10 , wherein a surface area of the convexities is 10%to 50% of an overall occupied area of the circumferential surface of theanvil.
 13. The apparatus according to claim 10 , wherein a depth of theconcavities is in a range of 20 μm to 100 μm.
 14. The apparatusaccording to claim 9 , wherein the ultrasonic horn has a flatcircumferential surface.
 15. The apparatus according to claim 9 ,wherein a width of the circumferential surface of the ultrasonic horn isthe same as that of the anvil, and both edges of the circumferentialsurfaces of the ultrasonic horn and the anvil are cut off.